While I havent done 1x without a clutch on gravel, Ive done it on MTB for multiple builds and it works fine.
Narrow-wide chainrings help retain the chain a lot. And besides that, just put something on the stay for chainslap and call it good.
3 MTBs in my house have 1x without clutch. One has an RD from the mid90s, another from the mid00s, and the last is a newer Microshift Advent RD.
My gravel bike has the Ultegra RX RD and I have enganged then disengaged the clutch multiple times while riding to try and see the difference. At this point, its just something I take on faith.